package march.test_3_3;

import java.util.Scanner;

public class TestMain {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int[] dq = new int[n+1];
        dq[0] = 1;
        dq[1] = 1;
        dq[2] = 1;
        for(int i = 3; i <= n; i ++) {
            dq[i] = dq[i-1] + dq[i - 2];
        }
        System.out.println(dq[n]);
    }
}
